A radiotherapy apparatus for irradiating a radiation upon an affected area of a patient to perform medical treatment is known.
In the case where a radiation is irradiated upon an affected area of a patient by the radiotherapy apparatus, the position or the shape of the affected area is sometimes fluctuated by breath of the patient, and so on.
In order to irradiate a radiation upon an affected area organization while suppressing an influence of the radiation on a normal organization of the patient, there is a method that the radiation is intermittently irradiated only in the case where an affected area organization is moved to an irradiation position of the radiation.
However, since the time of medical treatment is prolonged by such a method as just described, a heavy burden is imposed on the patient. Further, where the sum total of the energy amount of an irradiated radiation is constant, the effect of medical treatment increases as the irradiation time decreases. Hence, the method described above has the possibility that a biological effect (medical treatment effect) may decrease.
Therefore, another method is known that, by predicting the movement of the affected area position, the irradiation position of a radiation is moved to follow up the affected area position to irradiate a radiation.
It is to be noted that, as an existing technique relating to a radiotherapy apparatus, a method of controlling the irradiation timing for radioscopic image capture and a startup timing of a medical treatment radiation to acquire a radioscopic image in which a subtle shading difference is secured, another method of predicting the most likely certain affected area position at a point of time of medical treatment radiation irradiation based on time series data to accurately and securely irradiate a radiation upon the affected area, and a further method of comparing an acquired radioscopic image of an irradiation target with a reference image regarding a specific evaluation factor to carry out irradiation control with high reliability for an irradiation target and so forth are known.
[Patent Document 1] Japanese Laid-Open Patent Publication No. 2006-51199
In the conventional method described above, for example, prediction is carried out by simply applying an autoregressive model to an input time series signal obtained from an observation signal of an affected area position used as an input. Such prediction as just described is used, for example, when the affected area position after a very short period of time (for example, approximately 0.15 seconds) is predicted.
Further, in the method described above, in order to move the irradiation position of a radiation to follow up the affected area position, for example, the shape and the size of a passage window of a collimator for forming an irradiation range of a radiation are controlled.
However, there is the possibility that, if the time required for control of a collimator becomes long, then the shape and the size of the collimator cannot be controlled to the desired shape and size within a period of prediction time assumed for an autoregressive model, and as a result, irradiation following up the movement of an affected area position cannot be implemented.